Starting device

ABSTRACT

A starter device for internal combustion engines is proposed that comprises a drive mechanism ( 16 ) and a gearing ( 22 ) having a variable gear ratio, which said gearing is situated after the drive mechanism ( 16 ). The starter device ( 10 ) is characterized by the fact that the gear ratio of the gearing ( 22 ) is infinitely variable.

BACKGROUND OF THE INVENTION

The invention concerns a starter device for internal combustion enginesaccording to the general class in the independent claim. A starterdevice is made known in DE 199 27 905 A1, which said starter devicecomprises a gearing between a drive element and a pinion, which saidgearing has a variable gear ratio. The gearing is a planetary-gear set,the sun gear of which is capable of being driven by the drive element.The output of the planetary-gear set takes place via the planet gearsand, therefore, via the planetary carrier. The planetary-gear set makestwo different gear ratios possible: in the case of the first gear ratioat low speeds, gear reduction takes place via the internal ring gear,which is held stationary by means of an overrunning clutch. When thedrive mechanism reaches a certain speed, a plurality of centrifugalclutch elements attached to the planetary carrier cause the internalring gear to be held stationary with the planetary carrier; this causesthe planetary-gear set to be shifted from gear reduction to a one-to-onegear ratio. The disadvantage of this embodiment is the fact that theassistance provided to run the internal combustion engine up to speed isadjusted optimally at only two operating points.

ADVANTAGES OF THE INVENTION

The starter device according to the invention having the feature of themain claim has the advantage that the starter device can be adjusted asfavorably as possible for the operating states of the internalcombustion engine during start-up by means of the variable gear ratio ofthe gearing. As a result, the assistance provided by the starter deviceto run the internal combustion engine up to speed is optimal.

The continuously-variable design of the gearing leads to reduced wearand reduced noise in the gearing, because no force or load peaks occurhere when the gear ratio is changed. Advantageous further developmentsof the starter device according to the main claim are possible due tothe measures listed in the dependent claims. The expense required torealize the variable gear ratio in the case of the starter device isparticularly low when the gearing is self-regulating. Sensors, adjustingdevices, and expensive control technology can be eliminated.

SUMMARY OF THE DRAWINGS

Exemplary embodiments of a starter device according to the invention areshown in the drawings.

FIG. 1 shows a schematic view of a starter device according to theinvention.

FIG. 2 shows a spacial sectional detail view of the torque-controlledgearing,

FIG. 3 shows a spacial sectional detail view of the speed-controlledgearing,

FIG. 4 shows a spacial view of the coupled planet gears.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A starter device 10 is shown FIG. 1, which said starter deviceaccommodates a plurality of assemblies in a housing 13. The assembliesinclude the drive mechanism 16 that drives an output shaft 25 via aninput shaft 19, and a gearing 22. A pinion-engaging drive mechanism 28is supported on the output shaft 25 in rotating-slideable fashion. Thepinion-engaging drive mechanism 28 is capable of being engaged with anot shown ring gear of an internal combustion engine by means of asolenoid switch 31.

A first exemplary embodiment of the gearing 22 is shown in FIG. 2. Thisfirst exemplary embodiment is a gearing having a variable gear ratio,and the gear ratio is continuously-variable. The gearing 22 is designedas a planetary-gear set. A center gear 34 having a double-componentdesign is driven via the input shaft 19. The center gear 34 is composedof a first side gear 37 and a second side gear 40. The first side gear37 and the second side gear 40 each comprise side surfaces 43 that faceeach other, between which said side surfaces at least one planet gear 46can be held tightly. A further gear element is the internal gear 49,which also has a double-component design. The internal gear 49 iscomposed of a first side internal gear 52 and a second side internalgear 55. Both the first and second side internal gears 52 and 55 haveside surfaces 53 that face each other. One flange element is situated oneach side of the planet gears 46, and an output flange 58 is integrallyconnected to the output shaft 25 on the output end. An annular inputflange 61 is arranged on the input end. The output flange 58 and theinput flange 61 are interconnected in torsion-resistant fashion. Thistorsion-resistant connection is obtained by arranging opposing bores 64in the output flange 58 and the input flange 61. Bolts 67 are insertedthrough said bores for connecting purposes. The output flange 58 and theinput flange 61 are interconnected in torsion-resistant and axiallynon-displaceable fashion.

The input flange 61 as well as the output flange 58 comprise radiallyoutwardly extending grooves 70 on their circumferences. These grooves 70allow the axles 73—on which the planet gears 46 are securely arranged—toslide radially outwardly or radially inwardly in them.

The input shaft 19 comprises a shaft section 76 in which a helicalspline 77 is machined. The helical spline 77 is limited on both ends bytwo circlips. The first circlip acts as a stop for the first side gear,and the other circlip acts as a stop for the second side gear. The firstside gear 37 comprises a center bore in which a helical spline 77 ismachined as well. The first side gear 37 further comprises a cylindricalouter section 80 in which straight teeth are machined. The outer section80 lies radially within the planet gears 46. The second side gear 40 isplaced on the outer section 80 having the straight teeth 81, which saidside gear comprises an internal straight toothing that matches thestraight teeth 81 and meshes with them. In a first variant, the secondside gear 40 comprises an axially extending, cylindrical section 84facing the drive mechanism, which said section can be displaceablysupported with its exterior in a bore 86 of the input flange 61. In asecond variant, the cylindrical section 84 can extend only into theinput flange 61—due to spacial considerations—without transferringbearing forces here. The motion of the second side gear is hindered bymeans of the other circlip via a plate washer arranged at the end of thecylindrical section 84.

The internal gear 49 encompasses—with the first side internal gear 52and the second side internal gear 55—the at least one planet gear 46.The second side internal gear 55 is thereby supported in moveablefashion within the first side internal gear 52. The second side internalgear thereby bears against an internal retainer 95 by means of a springelement 93. The first side internal gear 52 is supported in displaceablefashion within the housing 13. The at least one planet gear 46 has abiconical design overall, and the planet gear 46 comprises an outwardlydirected conical surface 47 on each of its rotational-axial ends.

The function of the starter device 10—particularly the gearing 22—willbe explained hereinbelow. The starting position of the gearing 22 is asfollows: The drive mechanism 16 does not yet apply input torque, so theplanet gears 46 assume their radially innermost positions. This is dueto the spring element 93, which presses on the second side internal gear55, by way of which the first side internal gear 52 comes to bearagainst the planet gears 46. Due to the conical surfaces 47 and theforces acting on the conical surfaces 47 by the side internal gears 52and 55, this leads to a radially inwardly directed force on the planetgears 46; the planet gears 46 assume their radially innermost positions.

After the starter device 10 is started, the input shaft 19 begins torotate anticlockwise. Due to the helical spline 77, the first side gear37 is drawn in the direction toward the drive mechanism 16. The firstside gear 37 thereby presses with its side surface 43 against theconical surface 47 of the planet gear 46 and moves it in the directiontoward the side gear 40 until said side gear comes to bear against oneof the side surfaces 43 there. Since the sliding motion on the helicalspline 77 has now stopped, input torque from the drive mechanism 16 istransferred to the center gear 34, which said center gear now drives theplanet gears 46. The planet gears 46 thereby roll with their conicalsurfaces 47 on the side surfaces 43 of the first and second sideinternal gears 52 and 55 as well. The side surfaces do not rotatetherewith; instead, they are axially displaceable. The planet gears 46thereby drive the output flange 58 and the input flange 61 via the axles73 and the grooves 70, so that output torque is transferred to thepinion-engaging drive mechanism 28 via the output shaft 25.

Due to the very high initial input torque in the case of drivemechanisms 16 designed as electric motors, this leads to high clampingforces between the first and second side gears 37 and 40. These clampingforces ultimately lead to the forces exceeding the spring forces of thespring element 93, so that the first and second side internal gears 52and 55 are forced apart. The planet gears 46 walk radially outwardly.This leads to a situation in which, based on the axles 73 and [numeralmissing?], the planet gears 46 cover an ever-increasing rolling circle,which finally reaches a maximum. The reverse applies for the pitch linesbetween the first and second side internal gears 52 and 55 and theplanet gear 46. Here, the radius, i.e., the distance between the centerline of the axles 73 and the pitch lines, becomes smaller and smaller.The significance of this for the speed ratios that occur between theinput shaft 19 and the output shaft 25 is that, when the planet gears 46initially lie radially inwardly, the output shaft 25 rotates rapidlycompared to the input shaft 19. When the planet gears 46 move furtheroutwardly, the kinematic relationships then change in such a fashionthat the speed of the output shaft 25 decreases compared to the initialsituation.

Assuming a constant drive power of the drive mechanism 16, thesignificance of this for torque output by the output shaft 25 is thatthe torque at the output shaft 25 increases as the planet gears 46wander further outwardly. This is favorable in terms of startinginternal combustion engines, because said internal combustion enginesrequire a particularly high amount of torque at the beginning of thestarting procedure.

Once the internal combustion engine has broken away, the torque demandof the internal combustion engine drops continuously. As a result, thedrive mechanism 16 need not deliver as much input torque via the inputshaft 19 to the gearing 22, either. Consequently, this leads to areduced force in the helical spline 77 and, therefore, to lesser forcesbetween side faces 43 of the first side gear and the second side gear 37and 40. The force of the spring element 93 now becomes greater than theforce acting on the spring element 93 from the helical spline 77, sothat the side faces 43 of the first side internal gear 52 and the secondside internal gear 55 press on the conical surfaces 47 of the planetgears 46 with greater force than the force between the side surfaces 43of the first and second side gears 37 and 40. As a result, the planetgears 46 move radially inwardly along the grooves 70 once more, so that,on the one hand, the torque at the output shaft 25 decreases and, on theother hand, the speed of the output shaft 25 increases.

The second exemplary embodiment of the gearing 22 is shown in FIG. 3. Incontrast to the gearing 22 shown in FIG. 2, this exemplary embodiment isregulated according to the drive speed of the drive mechanism 16. Theinput shaft 19 has a positive contour via the shaft section on which thecenter gear 34 is arranged, which said contour meshes with a matchingpositive counter-contour of the center gear 34. These two positivecontours make an axial displacement of the center gear 34 on the inputshaft 19 possible. The center gear 34 also comprises a first side gear37 with the side surface 43. The side surface 43 of the first side gear37 cooperates with a second side surface 43 that is part of a surface ofa center ring 98. The center ring 98 is held on the center gear 35 bythe fact that said center gear 34 bears against a retainer 104 securedto the first side gear 37 via a spring element 101. The side surfaces 43of the center ring 98 and the first side gear 37 encompass a pluralityof planet gears 46 which are encompassed by the side surfaces 43 of aninternal gear 49 on their radial exterior, as is the case with the firstexemplary embodiment. The internal gear 49 is designed analogously tothe first exemplary embodiment. A plurality of bores 64 is machined inthe output flange 58, in which bores a plurality of bolts 67 is secured.The bolts 67 carry a planetary gear carrier 107 which is arranged on theside of the center gear 34 facing the drive mechanism 16. The planetarygear carrier 107 carries a multiple-component swivel arm 109 on thebolts 67, refer to FIG. 4 as well. The swivel arm 109 is arrangedbetween the output flange 58 and the planetary gear carrier 107. Theswivel arm comprises two individual arms 111, each of which comprisesthree individual openings along their length. The openings are alignedwith each other in each case. The center openings serve to support theplanetary gear carrier 107 on the bolt 67. Two lower openingsaccommodate an axle 113, to which a counterweight 114 is secured. Twoupper openings accommodate the axle 73, on which the planet gear 46 issituated. The planet gear 46 is held between the two individual arms111.

The function of the second exemplary embodiment will be explained usingFIGS. 3 and 4. If the input shaft 19 of the drive mechanism 16 isdriven, the center gear 34 is rotated simultaneously. The planet gears46 are driven via the side surfaces 43 of the first side gear and thecenter gear 98 via frictional forces. The planet gears 46 thereby rollon the side surfaces 43 of the internal gear 49 in an already-knownfashion. If the speed of the output shaft 25 is relatively low at first,the side surfaces of the center gear 34 initially force the planet gears46 radially outwardly with assistance from the spring element 101. As aresult, the spring element 93 of the internal gear 49 is loaded. Theoutput torque at the output shaft 25 is therefore relatively highinitially and serves to break away or start the internal combustionengine. If the speed of the output shaft 25 then increases, this meansan increase in the angular speed of the planetary gear carrier 107 and,therefore, an increase in the angular speed of the counterweights 114 aswell. Due to the kinematic relationships at the swivel arm 109, theincreasing centrifugal force of the counterweights 114 leads to anincreased axial force in the center gear 34, so that the side surfaces43 of the center gear 34 are forced apart. The kinematic relationshipsin the gearing 22 therefore change as well, so that planet gear 46therefore moves radially inwardly once more, and the speed of the outputshaft 25 increases over-proportionally to the speed of the input shaft19.

1. A starter device for internal combustion engines comprising a drivemechanism (16) and a gearing (22) having a variable gear ratio, whichsaid gearing is situated after the drive (16), wherein the gear ratio isinfinitely variable.
 2. The starter device according to claim 1, whereinthe gearing (22) is self-regulating.
 3. The starter device according toclaim 1, wherein the gearing (22) is capable of being regulatedaccording to a input torque of the drive mechanism (16).
 4. The starterdevice according to claim 1, wherein the gearing (22) is capable ofbeing regulated according to a drive speed of the drive mechanism (16).5. The starter device according to claim 1, wherein the gearing (22) isa planetary-gear set with a center gear (34) having at least one planetgear (46) and a internal gear (49), and wherein a radial actuating forceacting on the at least one planet gear (46) can be achieved by means ofthe input torque.
 6. The starter device according to claim 1, whereinthe gearing (22) is a planetary-gear set with a center gear (34) havingat least one planet gear (46) and a internal gear (49), and wherein aradial actuating force acting on the at least one planet gear (46) canbe achieved by means of the drive speed.